Hi, Jari, See comments inline: On Jun 26, 2010, at 4:11 AM, Jari Arkko wrote: > Thanks for your review, Ben! > >> -- 5.3.1, last paragraph: "In the case where the DNS options of RDNSS and DNSSL can be obtained >> from multiple sources, such as RA and DHCP, the IPv6 host can keep >> some DNS options from RA and some from DHCP; for example, two RDNSS >> addresses (or DNS search domain names) from RA and one RDNSS address >> (or DNS search domain name) from DHCP." >> >> This seems underspecified. For example, can it choose the last value from each? How is the host to guess which to keep? How can an administrator get predictable behavior? Mixing some from one source and another from the second seems, on the surface, like the worst possible behavior. Since using RA for this was described as an alternative for when DHCPv6 was not available, wouldn't it make more sense for dhcp to win? >> >> Furthermore, this makes me wonder if the concept here needs more thought. Under what circumstance would you be both doing stateless autoconfig and getting DHCPv6 for the _same_ interface? >> > > Let me speak with my "I deployed both mechanisms in my network" hat on :-) Sometimes you have to enable all possible mechanisms on the network side to make sure that your Windows/Apple/Linux/BSD computers and various appliances have a maximum chance of operating correctly. > > But lets talk about the issue of underspecification. I think some of that is intentional, because I don't think we should specify a hard limit on the number of servers specified or the number of sources the information can come from. > > However, I think I agree with you that it would be good to provide some predictability and make the language also tighter in other ways. And I don't think we can rule the DHCP side of this out of scope, because the DHCP RFC did not specify the interaction. How about this: > > OLD: (From Paul's new version) > In the case where the DNS options of RDNSS and DNSSL can be obtained > from multiple sources, such as RA and DHCP, the IPv6 host can keep > some DNS options from RA; the sufficient number of RDNSS addresses or > DNS search domain names is determined as a reasonable number (e.g., > three) by the local policy. On the other hand, for DHCP DNS options, > the DHCP configuration determines the number of DNS options > advertised to IPv6 hosts, so the sufficient number is out of scope in > this document. With these sufficient numbers of RDNSS addresses and > DNS search domain names, the DNS options from RA and DHCP are stored > into DNS Repository and Resolver Repository in the order that the > latest received RDNSS or DNSSL is most preferably used for DNS > queries. > NEW: > In the case where the DNS options of RDNSS and DNSSL can be obtained > from multiple sources, such as RA and DHCP, the IPv6 host SHOULD keep > some DNS options from all sources. Unless explicitly specified for the > discovery mechanism, the exact number of addresses and domain names to > keep is a matter of local policy and implementation choice. However, > it is RECOMMENDED that at least three sets of addresses and domain names > can be stored from at least two different sources. The DNS options from Router > Advertisements and DHCP SHOULD be stored into DNS Repository and Resolver > Repository so that information from DHCP appears there first and therefore > takes precedence. > That last SHOULD helps a lot, as it does seem to give more predicability. But I'm still having trouble with how this fits together. We are talking about the configuration for a particular interface on the host, right? I admit to not being an expert in DHCPv6, but: If the host wants (or is told) to use DHCP to get the DNS configuration, it made an explicit decision to send a DHCP request, right? That is, it's not getting this sort of thing from the DHCP server unsolicited? If it requests the info from DHCP, and gets it, why would it even pay attention to the DNS info from an RA? The part I still find under specificed is whether or not there are further management considerations for mixing and matching between DHCP and RAs. For example, is there a need to coordinate what is sent in DHCP and in RAs so that they don't conflict. As an extreme example, is there any expectation that a DNS server assigned via DCHP and another assigned in an RA would return the same response for a given DNS query? I will yield to your expertise if this is just a matter of me not understanding how DHCPv6 works. Or if such questions are simply out of scope, it might make sense to mention that. Same if they are discussed in some other draft or RFC. Thanks! Ben. > Jari > > _______________________________________________ > Gen-art mailing list > Gen-art@xxxxxxxx > https://www.ietf.org/mailman/listinfo/gen-art _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf